The present invention disclosed herein relates to a wireless communication system, and more particularly, to a method of correcting a time misalignment between envelope and phase components of a signal.
Modern wireless communication systems use complex modulation schemes to obtain higher data transmission rates within limited frequency resources. Owing to this, a transmission signal has a high peak-to-average power ratio (PAPR) that is a hostile condition for a power amplifier (PA) to obtain high efficiency. Also, since a today's base station tends to be miniaturized, a request for a PA structure of high efficiency is increased.
An envelope elimination and restoration (EER) structure is one of the highly efficient PA structures, and, in order to obtain high efficiency, has a structure of separating envelope and phase components of a signal, processing them respectively, and recombining them. Typically, an EER structure means a Kahn structure, but all structures, such as an improved Kahn structure or a digital polar modulator structure, separating envelope and phase components and processing can be considered as the EER structure. Among the EER structure, a structure applying a delta-sigma modulator (DSM) to an envelope component is called as an envelope delta-sigma modulator (EDSM) structure.
For any EER structure, a time misalignment of the envelope and phase components is directly connected to signal quality degradation. Since it is highly possible that the time misalignment of the envelope and phase components occur while they are separately processed, it is necessary to correct this time misalignment.